This invention relates to foot prostheses in general, and specifically to a prosthetic foot characterized by a unitary foot and heel construction, and/or an auxiliary ankle construction which permits the flexibility of the prosthesis to be selectively determined and easily changed. The invention also includes an improved coupling for attaching said foot prosthesis to an auxiliary pylon tube.
The prior art is replete with various types of mechanical devices purporting to solve the foot prosthesis problem. Typical of early devices is Lange U.S. Pat. No. 2,075,583, which incorporates a rubber form mounted in operative relationship with a rigid metallic core. Exemplary of the latest developments in the field is Poggi U.S. Pat. No. 4,645,509, which teaches a prosthetic foot incorporating a monolithic keel or beam of relatively massive proportions intended to react to the load of an amputee's body during walking, running, jumping, and the like and to release the resultant stored energy to create foot lift and thrust complementing the amputee's natural stride.
However, each of the prior art devices has significant deficiencies; specifically, the component parts of the prosthesis, as in Lange, are too heavy and too rigid or, as in Poggi, are too massive and monolithic to respond properly to the nuances of stress-response gradients characteristic of the human foot.
One of the primary factors which has inhibited the creation of a truly successful prosthetic foot has been the fixation of the prior art with the duplication of the structural aspects of the skeletal and muscular components of an actual human foot. In many instances, as exemplified by Poggi '509 mentioned hereinabove even the toes of the foot are attempted to be duplicated by providing simulacra thereof. It is this fixation upon the mechanical elements of the human foot which has restricted the art to an attempt to duplicate the human foot components, a tendency which is particularly exemplified in Gajdos U.S. Pat. No. 3,335,428.
My copending application Ser. No. 07/293,824, now U.S. Pat. No. 5,037,44 discloses certain concepts relating to a prosthetic foot characterized by a forefoot portion and a heel portion which may be permanently or demountably associated with each other whereby both the forefoot portion and the heel portion can be readily exchanged with correspondingly constructed heel and forefoot portions. This exchangeability permits size adjustment or accommodation of different spring rates to suit the size of foot of the amputee or the stride and weight of the amputee, yielding an almost infinite range of combinations of spring rate and size to the amputee, and allowing a natural stride and resilience of gait which has not been obtainable by prior art prosthetic devices. Other than my present invention and my copending application, I am unaware of any prosthetic foot device incorporating such demountably attached forefoot and heel portions, and providing such ease and range of adjustability.